There is a technology on the rise that has people talking "killer application" called Geotagging.   Geotagging is the process of attaching or encoding metadata onto media such as videos, photos, websites etc., which contains location coordinates.  Information such as GPS coordinates or even an address can be encoded into the content for a variety of purposes both useful and sinister. 

Knowing the location of where a piece of information originated (or has traveled) could be useful to location-based applications and information gathering sites, search engines etc. that could use location-based metadata to obtain information.   For instance, I could see the typical digital camera containing a GPS receiver that would automatically tag each photo taken with the exact location at which it was taken.  This would be useful for those of us who have loads of family photos but aren't exactly sure where we were when we took them.   We took a trip to Yellowstone a couple of years ago, and looking back at all the pictures of waterfalls and hot springs, there is no way to tell which one was which.   Goetagging certainly would come in useful here. 

From a forensics standpoint, there are some useful legal reasons why we would want geotagging.   Perhaps such information could be used to not only tag content origins, but also tag the locations where it has been.   Today, the ultimate Geotag is a vehicle Fastpass used for paying tolls.   This last summer I returned from my kid's Boy Scout camping trip to a moving violation I received in the mail.    The moving violation was for a place far from where I truly was at that time.   Using the Fastpass records for my vehicle, I was able to prove my innocence.   I remember saying at the time however, how difficult it would have been to prove my innocence if I had just been home watching a movie....

I can see a downside to geotagging as well though.   If such information were to fall into the wrong hands, people could exploit it and bosses could find out where you really are when you get on a conference call.   Yet, information is a two-edged sword: we can live and die by it.

Ultimately, I can see geotagging being useful, but I don't think I would go so far as to call it a "killer" and I certainly don't see application value in the actual tagging itself.   The usefulness comes after the fact and may have greater value to historians many years from now than it will have in our immediate future.